Universal leadframe carrier

ABSTRACT

A leadframe carrier and insert compatible with a temperature-affectable, expandable and contractable leadframe strip to be bonded with a selected plurality of semiconductor chips, said carrier being automatically separable and removable with regard to said insert during manufacture despite possible clinging which may be induced by the expansion and contraction of said carrier insert.

This application is a division, of application Ser. No. 07/170,069filed, Mar. 3, 1988 now U.S. Pat. No. 4,815,595 which is a continuationof 06/937,558, filed Dec. 3, 1986, - (now abandoned.)

TECHNICAL FIELD

This invention is directed toward the technical field of manufacturingsemiconductor chips, and more particularly to their automatedmanufacture, including the automated bonding of leadframe leads to thechips.

BACKGROUND ART

In the automated manufacture and packaging of semiconductor chips, chipsare made in batches instead of individually. Leadframes are typicallymade from strips or ribbons of flat sheets of conductive material, whichis divided into a predetermined selected number of individualleadframes, each of the leadframes defining a plurality of leads sixteen(16), for example, which are bonded to pads on the semiconductor chip.

To handle these strips of leadframes during automated manufacture, it isuseful to have a fixture which effectively holds individual strips ofthe leadframe together with the chips for bonding. One such fixture iscalled a leadframe carrier. These leadframe carriers can besystemmatically moved from station to station during manufacture on abelt or pressurized air, for example.

At present, the leadframe carrier is typically a custom device used forone particular kind of leadframe, which in turn corresponds in manycases to only a single kind or type or group of types of semiconductorchips. Accordingly, it is considered desirable to develop a leadframecarrier fixture which is conveniently adaptable to accommodate any ofmany different kinds of chips and leadframes.

DISCLOSURE OF INVENTION

According to the invention addressed herein, the leadframe carrierincludes an insert which fits between the upper and lower portions ofthe main carrier assembly.

The fixture insert is made to defined dimensions of length and widthfrom a flat, rigid sheet of conductive (e.g., metallic) material. Thespecific material used is selected to accommodate temperature-relatedexpansion and contraction of the leadframe material carried by theinsert. According to one version of the invention, both leadframe andinsert are made of a selected copper alloy. Formerly, the leadframecarrier and the leadframe itself would expand and contract withtemperature by different amounts, creating a poor fit between carrierand leadframe during manufacture.

Further, a feature of the carrier insert is its being coated with amaterial such as Teflon, a trademark owned by DuPont. This materialpermits the easy, nonclinging separation of leadframe and carrier, whenthis is desired during manufacture.

The leadframe carrier itself has upper and lower parts which can beclamped together to hold a strip of leadframe and the insert holding thechips to be bonded to the leads of the leadframe. Clamping can forexample be magnetic.

The foregoing and other objects, features and advantages of the presentinvention will become more apparent from the following description ofthe best mode for carrying out the invention and the accompanyingdrawing.

BRIEF DESCRIPTION OF DRAWING

The Figure shows isometrically in exploded view the top and bottomportions of a leadframe carrier and the chip carrying insert accordingto the invention herein.

BEST MODE FOR CARRYING OUT THE INVENTION

The Figure shows a leadframe carrier 12 including bottom and top orupper and lower, as the case may be, portions 13 and 13'. Further shownare a leadframe 33 and carrier insert 34, which is schematicallyindicated effectively to suggest its functional parts. Insert 34 fitsinto the bottom portion 13 of leadframe carrier 12.

Insert 34 holds a plurality of semiconductor chips 55 in a generallylinear configuration in recesses fashioned in the top surface thereof.

Semiconductor chips 55 are to be bonded onto the ends of inner leads ofthe leadframe 33 during manufacturing operation.

According to the invention, if chips 55 of a nonstandard or differentthan conventional size are to be bonded with leads from the same or amodified kind of leadframe; or if a different kind or size of leadframeis selected for bonding; then a different insert 34 according to theinvention can be used with the same universal carrier.

The lower carrier portion 13 defines holes 57 in its mass which reduceits overall weight, thereby making it lighter and easier to propelduring automated operations and to reduce the thermal load as seen bythe reflow medium.

Further, upper portion 13' of carrier 12 defines similar weight savingapertures of its own and further define a large central aperture 13",which permits the application of a heating vapor during manufacture, toeffect the solder bonding of leads from the leadframe to pads on acorresponding semiconductor chip 55. Pins in lower portion 13 help toalign and secure the leadframe during clamping together (whethermagnetic or otherwise).

As shown in the Drawing, the insert defines depressions of defined sizefor holding semiconductor chips 55 of corresponding size insertablytherein with their bonding pads upwardly disposed to meet the inner endsof leads from the leadframe. If larger (or smaller) chips are to be usedinstead, a different insert can be used, without requiring a new bottomportion 13 to be provided or otherwise fabricated.

As already suggested above, a single strip or ribbon of leadframeincludes many individual leadframes. Each leadframe in effect containsthe leads for a single chip. These leads are electrically shortedtogether during most of the manufacturing process, but are held togethercontiguously by a central perimeter from the same sheet material out ofwhich the entire leadframe ribbon is fashioned or fabricated. The leadsin effect traverse this perimeter, and those portions of the perimeterwhich are not part of a lead are ultimately cut away later inproduction.

Further, the individual chips 55 bonded to respective individualleadframes of the ribbon must of course be separated at the end ofmanufacturing operation.

The leads are in fact separated from one another after beingencapsulated in plastic, for example, during a late state of manufacturecalled trim and form. This breaks up the perimeter of leadframe materialwhich initially interconnects and holds together the leads duringbonding, handling and plastic molding.

It is the end of each inner lead of the leadframe which is bonded to acorresponding contact pad on the respective chip. The outer portion ofeach lead in turn extends out of the package, which may be made ofmolded or injected plastic or ceramic material as the case may be. Theouter portion of each lead is further typically bent and offset downwardas for insertion into a plug or socket as the case may be.

Each semiconductor chip is thus finally packaged with an array ofdownwardly disposed pins for insertion into or connector.

So-called leadless chip carriers are further also well known in theindustry. In the case of these, no pins extend downward to meet with amating plug or connector. Instead, the so-called leadless contacts arerespectively soldered directly onto predetermined locations on a printedcircuit board or chip carrier. The concepts of this invention are,however, applicable to either kind of package, leaded or leadless.

Individuals skilled in the art are likely to conceive of other versionsof the invention which are nonetheless a part thereof. Accordingly,attention is directed toward the claims which follow, as theseeffectively and legitimately define the bounds of the invention withparticularity.

What is claimed:
 1. A chip carrier insert for supporting semiconductorchips in alignment with groups of inner leads of a lead frame during amanufacturing operation in which lead frame inner lead end portions areto be bonded to bonding pads on the semiconductor chips with the chipcarrier insert and lead frame being sandwiched between first and secondlead frame carriers, said chip carrier insert being a strip ofconductive metal fabricated to predetermined dimensions of length andwidth to fit between the first and second lead frame carriers, saidstrip of conductive metal having surface portions adapted for retaininga plurality of semiconductor chips in bonding alignment with the endportions of a plurality of lead frame inner lead groups, respectively;aselected one of said lead frame carriers having first and secondshoulder portions spaced apart across an elongated channel, wherein saidstrip of conductive metal has length and width dimensions adapted to fitwithin the elongated channel between the first and second shoulders;and, a plurality of pins attached to said selected lead frame carrierand projecting into the elongated channel, said lead frame and strip ofconductive metal being intersected by a plurality of bores, wherein saidpins project through said chip carrier insert and through said leadframe for aligning the chip bonding pads with the lead frame inner endsand securing the selected lead frame carrier, chip carrier insert andlead frame together.
 2. A chip carrier insert as defined in claim 1,wherein said strip of conductive metal is characterized by a coefficientof thermal expansion which is matched with the coefficient of thermalexpansion of the lead frame.
 3. A chip carrier insert as defined inclaim 1, wherein said surface portions for retaining a plurality ofsemiconductor chips comprise a plurality of recesses having dimensionscorresponding with the dimensions of the semiconductor chips forreceiving each chip and retaining it with its bonding pads disposed tomeet the inner ends of leads from the lead frame.
 4. A chip carrierinsert for supporting semiconductor chips in alignment with groups ofinner leads of a lead frame during a manufacturing operation in whichlead frame inner lead end portions are to be bonded to bonding pads onthe semiconductor chips with the chip carrier insert and lead framebeing sandwiched between the first and second lead frame carriers, saidchip carrier insert being a strip of conductive metal fabricated topredetermined dimensions of length and width to fit between the firstand second lead frame carriers, said strip of conductive metal havingsurface portions adapted for retaining a plurality of semiconductorchips in bonding alignment with the end portions of a plurality of leadframe inner lead groups, respectively; and,a selected one of the leadframe carriers having first and second elongated shoulders disposed onopposite sides of an elongated channel, said chip carrier insert havinglength and width dimensions adapted for placement between said shoulderswithin the elongated channel, and with the lead frame being disposedbetween the chip carrier insert and the other lead frame carrier,wherein the other lead frame carrier is intersected by an elongatedcentral aperture which exposes the end portions of groups of inner leadsof said lead frame to contact by a heating vapor during manufacture, topermit the solder bonding of leads from the lead frame to bonding padson semiconductor chips mounted on said chip carrier insert.
 5. Auniversal lead frame carrier assembly including first and second leadframe carriers defining in combination an inner cavity for receiving achip carrier insert and a lead frame having a plurality of groups oninner leads, said chip carrier insert having surface portions adaptedfor retaining a plurality of semiconductor chips in bonding alignmentwith the inner lead end portions of the plurality of lead frame innerlead groups, said first and second lead frame carriers, said chipcarrier insert and said lead frame being fabricated to predetermineddimensions of length, width and depth to permit the chip carrier insertand lead frame to be assembled in stacked relation within the innercavity;a selected one of the lead frame carriers having first and secondelongated shoulders disposed on opposite sides of an elongated channel,said chip carrier insert having length, width and depth dimensionsadapted for placement between said shoulders within the elongatedchannel, and with the lead frame being disposed between the chip carrierinsert and the other lead frame carrier; and, the other lead framecarrier being intersected by an elongated central aperture which exposesthe end portions of groups of inner leads of said lead frame to contactby a heating vapor during manufacture, to permit the solder bonding ofleads from the lead frame to bonding pads on semiconductor chips mountedon said chip carrier insert.
 6. A universal lead frame carrier assemblyas defined in claim 5, wherein said chip carrier insert comprises astrip of conductive metal having a coefficient of thermal expansionwhich is matched with the coefficient of thermal expansion of the leadframe.
 7. A universal lead frame carrier assembly as defined in claim 5,wherein said chip carrier insert comprises a strip of conductive metalwhich is intersected by a plurality of recesses having dimensionscorresponding with the dimensions of the semiconductor chips forreceiving each chip and retaining it with its bonding pads beingpositioned to meet the inner ends of leads from the lead frame.
 8. Auniversal lead frame carrier assembly including first and second leadframe carriers defining in combination an inner cavity for receiving achip carrier insert and a lead frame having a plurality of groups ofinner leads, said chip carrier insert having surface portions adaptedfor retaining a plurality of semiconductor chips in bonding alignmentwith the inner lead end portions of the plurality of lead frame innerlead groups, said first and second lead frame carriers, said chipcarrier insert and said lead frame being fabricated to predetermineddimensions of length, width and depth to permit the chip carrier insertand lead frame to be assembled in stacked relation within the innercavity; and,a plurality of pins attached to a selected one of said leadframe carriers, said plurality of pins projecting into said cavity, andsaid lead frame and chip carrier insert being intersected by a pluralityof bores, wherein said pins project through said chip carrier insert andthrough said lead frame for aligning the chip bonding pads with the leadframe inner ends and securing the selected lead frame carrier, chipcarrier insert and lead frame together.